If your screening test detects a potential cancer, the next step is to confirm whether or not the suspicious area or polyp contains cancer cells, and if so, determine the extent (or stage) of the disease. Some tests you may have include:

Biopsy involves taking a sample of the suspicious growth or polyp for examination under a microscope and testing by a pathologist. A biopsy may be done during a colonoscopy or sigmoidoscopy.

Blood tests to check for carcinoembryonic antigen (CEA). Some people who have colorectal cancer or other conditions have a high CEA level.

Colonoscopy if it was not done previously.

Chest x-ray to determine whether cancer has spread to the lungs.

Computed tomography (CT) scan uses an x-ray machine linked to a computer to create a series of detailed pictures inside your body. You may receive an injection of dye to help certain areas show up better. A CT scan may detect whether cancer has spread to the liver, lungs, or other organs.

Endorectal ultrasound for rectal cancer uses an ultrasound probe inserted into the rectum to produce sound waves that humans can’t hear. The waves produce echoes, and a computer uses the echoes to create a picture. The picture may show how deep a rectal tumor has grown or whether the cancer has spread to lymph nodes or other nearby tissues.

Magnetic resonance imaging (MRI): A powerful magnet, radio waves, and a computer combine to make detailed pictures of inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI). An MRI might be performed to see whether the cancer has spread, or the local extent of the disease, such as in the case of rectal cancer.

Genetic testing: Examining the genes of your cancer, from the biopsy or through a blood test may indicate whether your colon or rectal cancer is caused by an inherited genetic syndrome such as Lynch Syndrome, Familial adenomatous polyposis (FAP) or MYH-associated polyposis. Although these conditions are very rare, your cancer care team may suggest you seek genetic counseling if you:

While knowing this information will likely not change your treatment plan, it may impact your follow-up and surveillance recommendations going forward, such as how frequently you may need a colonoscopy.